Booster pump with variable pitch auxiliary propeller



Dec. 22, 1942 R. R. CURTIS 2,306,300

BOOSTER PUMP WITH VARIABLE PITCH AUXILIARY PROPELLER Filed Dec. 24, 1941Patented Dec. 22 1942 BOOSTERWUMP WITH VARIABLE PITCH AUXILIARYPROPELLER Russell R. Curtis, Dayton, Ohio, assignor to Our is PumpCompany, Dayton, Ohio, a. corpor tion of Ohio Application December 24,1941, Serial No. 424,220

14 Claims. (01. 103-88) This application is a continuation in part of myco-pending application Serial No. 409,647 filed September 5, 1941.

The present invention relates to pump assemblies especially adapted foruse .in high altitude aircraft fuel systems for efllciently separatinggases and vapors from liquids so that only fully liquid material ispumped thereby.

More specifically, this invention relates to centrifugal booster pumpassemblies having auxiliary agitators with automatically adjustablevanes,

which feather down or flatten out when subjected to increased fluidresistance such as occurs When the agitators are speeded up. Theagitators effect cavitation in the liquid in which they operate foraiding in the beating out of bubbles and gas from liquid. The pumpassemblies include bell mouthed shaped guides for directing the liquidto be pumped to the agitators and for directing the separated gases andvapors out of the path of the incoming fluid and thus not only beat out,in bubble form, the occluded gases and vapors in the liquid but alsoinduce, in the cavities or pockets behind the vanes, the formation ofgas and vapor from the more volatile liquid ingredients.

In accordance with this invention, a pump casing is so mounted withrelation to a source of liquid, such as a fuel tank, as to be below thehydraulic gradient of the liquid. The casin has an inlet throatcommunicating with the source of liquid and a volute chamber receivingpressured liquid from the throat. An impeller disk having pumping vanesthereon centrifugally pumps the liquid from the throat to the volutechamber. an agitating propeller in spaced relation from the pumpingvanes and preferably at the inlet to the throat. A guide or shield ismounted in spaced relation from the inlet throat to direct liquid to theagitating propeller along a converging path. This path converges at arelatively high rate to a point spaced from the discharge end thereofand then converges from this point at a slowe yrate to the discharge endthereof. The

This impeller assembly also carries resultn. bellmouthed path has veryhigh fluid the area between the propeller and impeller and 55 starts theliquid to whirl so that when the liquid strikes the open edges of theimpeller vanes, only a negligible amount of vaporization can take place.

The outer face of the shield directs bubbles of gas and vapor from theagitating propeller out of the path of the incoming liquid so that thebubbles are not entrained. in the liquid entering the pump. At the sametime the liquid is delivered to the agitating propeller at a minimumpressure so that bubble formation at the propeller is enhanced.

It is preferred that the centrifugal booster pump of the typeillustrated and to be described herein be interposed in the fuel lineofa fuel system between the source of liquid, such as a fuel tank, and anengine-driven fuel pump. During normal operation in such a system, themain function of the booster pump is to beat out the gases and vaporsfrom the fuel and to merely pressure the beaten fuel sufliciently sothat additional bubbles will not be formed in the fuel line. The fuelpump itself in such normal operation, even at high altitudes, willpressure the fuel to the engine. When, for any reason, the engine-drivenfuel pump fails in operation, the centrifugal booster pump has theemergency duty of supplying the vehicle engine with fuel pumped eitherthrough the inoperative engine pump or by-passed therearound. In orderto meet such an emergency, the centrifugal booster pump must be operatedat higher speeds than for normal duty in order to produce higherdischarge pressures.

It has been found that effective vapor separation for high altitudeperformance can be ob- {tained when the blades of the propeller are setat a high pitch, even when the propeller is driven at low speeds.However, if the blade angle remains fixed as the speed is increased toproduce emergency pressure, the power requirement for driving both theimpeller and the propeller becomes excessive.

A variable pitch propeller is therefore provided in which the angle ofthe blades is auto-' matically reduced as the propeller speedisincreased.

It is, therefore, an object of this invention to provide a liquid pumpwith agitating means whose resistance to rotation in a liquid remainssubstantially constant during increases in the speed of rotation of theagitating means.

Another object of this invention is to provide a variable pitchagitating member for a centrifugal pump.

A further object of this invention is to provide a propeller foragitating a liquid having blades thereon whose pitch angle isautomatically reduced with changes in the speed of rotation thereof.

A still further object of this invention is to provide a propeller foragitating a liquid having pivotally mounted blades and cam meansassociated with the blades for automatically reducing the pitch anglethereof when the speed of rotation of the propeller is increased.Another and still further object of this invention is to provide a fuelpump with an agitating propeller having blades pivotally connected to adrive shaft and with spring pressed cams co-operating with the blades toregulate the pitch angle thereof in accordance with changes inresistance to rotation efiected by changes in the speed of rotation ofthe blades by the shaft.

A further object of this invention is to provide a booster pump having avariable pitch propeller ly ng above the mouth thereof with a bellmouthed shaped annular fluid guide shield which discharges fluid to theagitating propeller and which guides gas and vapor bubbles from thepropeller away from the pump inlet.

The novel features believed to be characteristic of the presentinvention are set forth with particularity in the appended claims. Theinvention itself,'however, both as to its organization and manner ofconstruction, together with further objects and advantages thereof, maybest be understood by reference to the following description taken inconnection with the accompanying drawing, in which:

Figure 1 is a broken and fragmental vertical cross-sectional view, withparts in elevation, of a booster pump, adjustable pitch propeller, guideshield, and fuel tank assembly all in accordance with principles of thisinvention;

Figure 2 is -a plan view of the booster pump, adjustable pitch propellerand guide shield assembly shown in Figure 1;

Figure 3 is an enlarged fragmentary vertical cross-sectional view, withparts in elevation, as seen when taken substantially in the plane in-'dicated by the line III-III of Figure 1 andshowing the operativerelation of a vane and a spring pressed cam for maintaining the pitchangle of ,the vane when the parts are either at rest or being rotated ata low speed;

Figure 4 is a view similar to Figure 3 showing the change in pitch angleof a feathered vane when the parts are being rotated at a high speed;and, v

Figure 5 is a view somewhat similar to Figures 3 and 4 illustrat ng. infull lines. the pitch angle of the propeller blade when the propeller isbeing operated at normal speeds and. in dotted lines, the featheredposition of the propeller blade when the propeller is be ng operated athigh speeds for emergency duty.

In Figure 1, the reference numeral l designates a fuel tank, vented asat Illa, and containing a pond P of liquid fuel. such as gasoline, Thebottom wall of the'tank has a circular aperture Itb therein and amounting ring i I mounted in the tank on its bottom wall around theaperture.

A booster pump l2, of the centrifugal type, is mounted on the tankaround the aperturein the bottom wall thereof. The booster pump includesa casing I3 defining a volute or pumping chamber I4 and a shaft housingIS. The casing I3 is connected with a source of' motive power (notshown) which drives the shaft IS in the housing portion l of the casing.The casing hasan outtumed annular flange H for mount- 21, at spacedintervals around the throat ring,

are threaded through the ring into the flanged portion ll to mount thering on the casing 13.

The throat ring 20 has a central aperture 22 therethrough for joiningthe interior of the tank It) with the volute chamber 14. The aperture 22flares outwardly as at 22a to provide an inlet mouth for the boosterpump.

A plurality of standards or ribs 23, each having a foot portion 231:,are disposed around the throat ring and secured thereon by the bolts 2|.The standards or ribs are fixedly secured at their upper ends to a bellmouth annular shield 24. The ribs 23 carry the shield 24 in spacedrelation above the throat ring 20.

The shield 24 has an inner face 240 which, as best shown in Figure 1,converges from the upper end of the shield at a relatively high rate toa point intermediate the top and bottom of the shield. The face thenconverges at a slower rate'from this point to the bottom or dischargeend of the shield. The inner face 24a has a smooth continuous curvatureespecially designed for a high fluid flow capacity without, however,unduly pressuring the fluid as the path converges to the discharge end.This particular curvature has greatly enhanced the pumping capacity ofthe booster pump since it flares outwardly at the inlet end thereof toreceive fuel from the pond P over a relatively large area and thenguides the fuel inwardly from this large area along a path having arelatively small vertical component to a point ahead of the dischargemouth of the shield. While the path continues to converge from thispoint it com. verges at a slower rate and thus does not materiallyincrease thepressure of the fuel for any given velocity. The reducedheight of the shield positions the inlet end thereof closer to thebottom of the tank so that the fuel even at low levels of the tank willenter the guide.

The-booster pump has an impeller assembly 25 mounted on the drive shaftIt. This imreller assembly includes a disk or flange portion 25 spanningthe inlet 0 aperture 22 in the throat ring and communica ng freelyaround the periphery thereof with the inner rim of the volute chamberl4. Curved pumping vanes 21 are mounted on the flange 26 around theperiphery thereof to' underlie the throat ring 20. These pumping vanes21 define, with the throat ring 20 and the flange 26, open ended pumpingchannels communicating at their outer ends with the volute chamber l4and at their inner ends with the inlet of the throat ring.

A hollow cap or fairing member 28 is pressed on or otherwise suitablysecuredto a cup mem ber 29 which has its inner periphery threaded forengagement with the threaded end of the shaft l6 and to which it isconnected by means of a cross pin 30. In this connected position, theoutwardly tapered cap member 28 seats on the impeller flange 26. The cupmember 29 has an upwardly extending shaft portion 3| for receiving atthe top end thereof a propeller assembly 32.

As best shown in Figure 2, the propeller assembly includes a hub member33 having substantially radially extending support portions 34 thereon.A propeller blade 35 is pivotally mounted on each of the supportportions 34 to extend outwardly therefrom and normal thereto.

Each of the blades 35, as viewed from the free end thereof, has arounded nose portion or leading edge 36 with the side surfaces 31 and 38tapering toward the rear thereof and terminating in substantially a lineedge. The inner ends of each of the blades 35 are of reduced.

outer ends of each of the blades 35 are recessed at 35a to receivetherein the head of a pivot pin 4] extending longitudinally through theblade and being threaded into or otherwise suitably secured to one ofthe support portions 34 of the mounted on the shaft portion 3|.

hub member 33. Each of the blades-35 is thereby pivotally mounted on thehub member for rocking movement in a plane substantially right angularlydisposed to the plane of rotation o the impeller assembly.

It will be noted that the rounded nose or leading edge 36 of each of theblades 35 faces in the direction of rotation of the propeller assembly.As best shown in Figure l, the hub member 33 and pivotally connectedblades 35 are secured to into the atmosphere anddischarge their vaporsor gases.

It should therefore be understood that the shield 24 serves twofunctions, namely, to increase the feed of liquid fuel to the pump andto guide the beaten out bubbles away from the incoming liquid fuel. Thecurvature of the inner face of the shield is designed so that the shieldcan be relatively flat, receive liquid from large area, and discharge itout of a smaller area atminimum pressure, so as not to interfere withthe bubble separation.

The bubble-freed liquid enters the pump through the inlet mouth 22 ofthe throat ring. It is then pressured by the impeller assembly into thevolute chamber.

It is preferred that the centrifugal booster pump illustrated anddescribed operate at a comparatively slow speed for producing lowdischarge pressures found to be most desirable for beating out bubblesof gases and vapors from' the liquid fuel and for pressuring thevapor-freed fuel into the fuel line whereby an aircraft may the shaftportion 3| and held in place thereon by means of a nut 42 threaded tothe free end of the shaft.

The blades of the propeller are'disposed in the space between the bottomof the shield 24 and the top of the throat ring 20. As shown in Figures1 and 2, the blades 35 extend across the entire discharge mouth of theshield 24.

A sleeve member 43, having a radially extending flange 44 at one endthereof, is slidably A coil spring 45 is interposed between the cupmember 29 and the flange 44 of the sleeve 43 to embrace the shaftportion 3| and seat within the upper hollow portion of the cap member28.

As shown in Figure 3, the coil spring 45 exerts pressure against theflange 44 to seat the flange aga nst the angularly'extending cam surface40 on the end portion of each of the blades 35. With the' parts sopositioned, each of the propeller blades 35 is disposed at a relativelysteep be operated at high altitudes. The usual fuel system for anaircraft to be operated at high altitudes includes an engine-driven fuelpump which receives the liquid fuel discharged into the fuel line by thebooster pump. Should the engine-driven fuel pump fail in operation. the

speed of the booster pump must necessarily be.

increased in order to deliver liquid fuel directly to the carburetor ofthe aircraft engine, either through the inoperative fuel pump or througha by-pass therearound. This higher rotating speed of the propellerfor'producing higher discharge pressures necessitates an excessive powerrequirement for driving both the propeller and the impeller. This is dueto the high pitch angle at wh ch the blades of the propeller are set toeffect the most efficient gas and vapor separation at low rotatingspeeds. Consequently, if the low pitch angle of the blades remains fixedas the speed is increased to produce emergency pressure, the powerrequirement becomes excessive.

This objection is eliminated by providing a propeller assembly which hasa high blade angle at low speeds with an automatic and gradual reductionin the blade angle as the speed is increased. This high pitch angle isillustrated in Figure 5 at A, and atnormal operation is less than 90,and is the included angle between the seated cam surface 40 and the flatflange 44 and a longitud nal axial plane B passed through a blade. When,the rotating speed of the propeller assembly'321 is j'increased overthe normal speed, the inertia of the liqui to agitation as it flowsdownwardly from the shield exerts a pressure'on agitate the fuel flowingdown through the shield 24 as soon as the fuel. is discharged from theshield. The propeller beats out of bubbles B gases and vapors from theliquid fuel and throws these bubbles outwardly from the discharge mouthof the shield where they can rise in the pond P along a path between theshield and .throat ring. The outer face 241) of the shield slopes uwardly and outwardly away from the throat ring so that the bubbles areguided away from the inlet to the shield. The bubble oath widens out andthe bubbles become larger as they approa ah the surface of the pond P.Upon reaching the surface of the pond P the bubbles burst the lower side38 of the propeller blades 35. This pressure tends to feather the bladesor, in other words, tends to move the blades to a horizontal position--in which the resistance to rotation is decreased. As seen in dottedlines of Figure 5,

i the blade when feathered at high or emergency the pitch angle of theblades between the maximum limits illustrated in Figure 5. When thespeed is such that the resistance pressure is greater than thecompression of the coil spring 35, the propeller blades will graduallyfeather to a horizontal or fiat position as illustrated in Figures 4 and5. As soon as the rotational speed is decreased, the resistance pressureagainst the surfaces 38 will likewise decrease and the propeller bladeswill gradually assume their greatest pitch angle as illustrated inFigures 1 and 3.

It will be apparent from the foregoing that a booster pump constructionis provided herein having a propeller assembly which is normallyoperated at low speeds to effect the .most eflicient gas and vaporseparation from a liquid, while at the same time pressuring the liquidsuiiiciently to effect a continual flow of the liquid to the carburetor.When higher pressures of liquid flow are desirable, the speed of theimpeller is increased. As the impeller and propeller have a commondrive, the speed of the propeller assembly is likewise increased and theblades are so mounted as to automatically feather to liminate anexcessive power requirement for driving the propeller. In the presentpropeller assembly, the blades are so mounted that the pitch anglethereof is automatically regulated in accordance with changes inresistance to rotation effected by changes in the speed of rotation ofthe blades with the drive shaft.

While a particular embodiment of this invention only has beenillustrated, it will, of course, be understood that the invention shouldnot be limited thereto, since many modifications may be made, and,therefore, it is contemplated by the appended claims to cover all suchmodifications as fall within the true spirit and scope of the presentinvention.

I claim as my invention:

1. In a pump construction having an inlet throat, a shaft extendingthrough said throat, a hub member on said shaft in the path of fluid tothe throat, propeller blades, means pivotally mounting said bladesradially on said hub to position the blades for acting on fluid beforeit enters the throat, a cam portion on each of said blades having anangular cam surface thereon, a cam member slidable on said shaft andhaving a surface for seating said cam portions of the blades, and springmeans urging said cam member toward said hub and against the angularsurface of said cam portions on the blades for normally maintaining eachof the blades at a steep pitch angle, said blades being feathered to areduced pitch angle when rotated at a speed whereby the fluid pressureon said blades is greater than the pressure exerted by said springmeans.

2. In a pump construction having an inlet throat, a shaft extendingthrough said throat, a hub member carried by the shaft on the inlet sideof the throat and having radially extending support portions, propellerblades each having a rounded leading edge and tapering rearwardlytherefrom, a pivot pin carried by each support portion for pivotallymounting each of the blades on the hub radially of the shaft to act onfluids entering the pump before the fluids become condinal axial planeof the blade is less than 90, a,

cam member slidable on said shaft toward said hub and having a surfacethereon for engaging said angular surfaces on the blades, and a coilspring embracing said shaft and exerting prescams, said blades beingfeathered to a reduced pitch angle when rotated at a speed whereby thefluid pressure on said blades is greater than the pressure exerted bysaid coil spring.

3. In a pump construction, a pump casing havin an inlet throat, animpeller with pumping vanes underlapping the throat, a guide shieldmounted in advance of the throat to define therein and therearoundlocalized flow paths, and a variable pitch agitating propeller betweensaid shield and said threat.

4. In a pump construction, a pump casing having an inlet throat, animpeller with pumping vanes underlapping the throat, a guide shieldmounted in advance of the throat to define therein and therearoundlocalized flow paths, a propeller between said shield and said throatfor agitating liquid flowing to said throat, said propeller havingindependentlymovable blades, and cam means normally maintaining each ofsaid blades at one pitch angle during rotation of the propeller below apredetermined speed, said blades being feathered to a reduced pitchangle when rotated at a speed whereby inertia of the liquid to agitationexerts a pressure on said blades sufficient to cause relativ movementbetween said cam means. 5. In a centrifugal type pump having an inletthroat, an impeller for pressuring liquid received from said throat, anagitating member for effecting cavitation in the liquids being fed tothe throat, and means for feathering said agitating member to vary thecavitation in the liquid.

6. In a centrifugal type pump having an inlet throat receiving liquidfrom a pond, an impeller for pressuring liquid received from saidthroat, agitating vanes adjustable relative to said impeller androtatable therewith and positioned to act on that portion of the liquidin the pond adjacent the throat for effecting cavitation in the liquidto liberate bubbles of gas and vapor from the liquid into the pond, andmeans for moving said vanes relative to said impeller in response tochanges in speeds of rotation of the impeller.

7. In a centrifugal type pump, an impeller for pressuring liquid,pivotally mounted agitating vanes co-supported with said impeller foreffecting cavitation in a liquid being fed to the impeller, and pressureexerting means for adjusting said pivotally mounted vanes to vary thecavitation in the liquid.

8. In a centrifugal type pump having a drive shaft, an impellerrotatable with said shaft for pressuring liquid, agitating vanespivotally mounted on said shaft and rotatable with the shaft foreffecting cavitation in a liquid being fed to the impeller, and meansfor feathering said pivotally mounted vanes relative to said shaft forvarying the cavitation in the liquid.

9. In a centrifugal type pump, an impeller for pressuring liquid, anagitator for acting on liquid being fed to the impeller, said agitatorincluding a hub and vanes rotatable with and adjustable relative to thehub for effecting cavitation in the liquid in which they operate, andmeans for adjusting said vanes relative to said hub to vary thecavitation in the liquid.

10. In a centrifugal type pump having a drive shaft, an impellerrotatable with said shaft for pressuring liquid, agitating vanespivotally mounted on the shaft and rotatable therewith for effectingcavitation in the liquid being fed to the impeller, and spring urged cammeans sensitive to pressure exerted on said vanes by the liquid beingagitated for feathering the vanes in accordance with the exertedpressure.

11. In a centrifugal type pump having an inlet throat, a drive shaftextending through said throat, an impeller rotatable with said shaft andpositioned for pressuring liquid from said throat, a hub portion on saidshaft in spaced relation from said impeller, agitating vanes pivotallymounted on said hub and extending radially with respect to said shaft,said vanes being rotatable with said shaft for effecting cavitation in aliquid being fed to said throat, a member slidable on said shaft betweensaid impeller and vanes, a coil spring for normally urging said slidablemember toward said vanes, and a cam on each of said vanes engageable bysaid spring urged member, said slidabie member, cams, and coil springcoacting to feather said vanes in accordance with pressures exerted onthe vanes by the liquid agitated thereby.

12; A pump construction comprising an inlet throat, pumping vanes on oneside of saidthroat, agitating vanes on the other side of said throat,and means for feathering said agitating vanes.

- ing an inlet throat for receiving fluids therethrough, an impelleradjacent the outlet side of said throat for pumping fluids received fromthe hroat, vanes adjacent the inlet side of said throat foragitatingfluids before entering the throat, means for co-rotating said impellerand said agitating vanes, and means for feathering said vanes inaccordance with pressures exerted thereon by the fluids agitatedthereby.

14. A centrifugal type pump construction comprising an inlet throat forreceiving fluids therethrough, a drive shaft extending through saidinlet throat, an impeller rotatable with said shaft adjacent the outletside of said throat for pumping fluid's received from the throat, vanesrotatable with said shaft adjacent the inlet side of said throat foragitating fluids before entering the throat, said vanes being pivotallymounted on said shaft for rotation about their own axes, and pressureexerting means for feathering said vanes about their own axes inaccordance with pressures exerted thereon by the fluids agitatedthereby.

RUSSELL R. CURTIS.

